Maintaining and controlling fluid flow is important in many apparatus and procedures, including medical procedures, in order to ensure that a fluid medication is delivered to a particular location, such as from a fluid source into a subject patient. In delivering a fluid to a patient through a fluid administration system, it is often important to ensure that the fluid moves in one direction, generally from the fluid source to the patient, due to myriad problems that can arise should fluid flow be reversed during an injection procedure. In order to prevent the reversal of fluid flow, many fluid administration systems include check valves. A check valve may be disposed within a fluid flow passageway and include structure that may only allow fluid flow in a first direction, while preventing any fluid flow in an opposite, second direction. Certain conventional check valves may include a mechanism to allow fluid flow in the reverse direction. However, for safety purposes, the check valves that are included in medical apparatus generally allow fluid flow only in a first direction, from fluid source to patient.
A common problem of conventional check valves is that upon reversal of liquid flow through tubing in a direction from a patient to a fluid source, the check valves fail to respond as quickly as desired to move into a closed position. Further, many conventional check valves require some positive action by an operator to open a check valve, and another positive action by an operator to close the check valve. In a procedure, such as a medical injection procedure, this increases the risk that a check valve may inadvertently be left in an open position. That is, should such conventional check valves be used, there is always the risk of backflow from the output to the input of the fluid administration system, which in many instances is very undesirable, and in some cases, may even be fatal.
Thus, it can be seen that preventing fluid flow from the output to the input of a fluid administration system can be very important. As a result, valves in medical injection systems may be made to be normally closed, whereby the valve, in order to remain open, must be subject to a high flow pressure. When fluid flows from the fluid source to the patient in the forward direction, the flow pressure moves the valve to an open position to allow such flow. When the flow pressure is decreased, the valve will quickly close. However, as will be explained in greater detail below, there are many instances in which an operator may wish to open a check valve in order to reverse fluid flow from the output to the input. The normally closed types of fluid check valves used in medical procedures do not allow for the valve to be opened in these instances.
As mentioned briefly above, during an injection, fluid flow is required to be directed into a patient. The procedure generally involves directing fluid flow from a fluid input device, such as a syringe, through a delivery tube, then into and through a fluid output device, such as a catheter, to deliver a particular fluid into a subject patient. During the setup of the injection system, a medical technician will need to confirm that a catheter which is inserted into a patient is in the correct position. The technique used to determine correct catheter placement is for the syringe plunger to be momentarily retracted until blood is detected in the tube, thereby confirming correct catheter placement in a blood vessel. With the standard normally closed check valves in place in current fluid administration systems, backing up the syringe plunger and thus drawing a fluid, such as blood, through the catheter and into the delivery tube is impossible.
Another problem with the use of normally closed check valves in a fluid administration system is that some syringes require returning the plunger to the starting position of an injector following injection in order for the syringe to be removed from the injector. As described above, the standard normally closed check valves prevent retraction of the syringe plunger. Thus, in current injection systems, the delivery tube including the check valve requires disconnection from the syringe in order to retract the plunger up to its starting point for removal of the syringe. The removal of the delivery tube has the potential to expose the medical technician to biohazards, such as blood or other bodily fluids.
An example of check valves as used in medical fluid administration systems is disclosed in U.S. Pat. Nos. 5,743,872 and 5,665,074 by Larry Kelly and assigned to Liebel-Flarsheim Company of Cincinnati, Ohio. The '872 and '074 patents disclose a limited backflow reflux valve for connection between a syringe, catheter, and bulk container of injection fluid. This reflux valve permits injection of fluid from the syringe through the catheter into the patient, and also permits refilling of the syringe from the bulk container without disconnection of any tubing. Although the reflux valve also permits limited volume of fluid to backflow from the catheter into the syringe, so that the catheter may be checked for patency, it prevents any further backflow along this path after a limited volume has been allowed. Thus, such a limited backflow reflux valve, as in the '872 and '074 patents, would not allow the reversal of fluid flow such as would be required to allow a syringe plunger to be completely backed up within the fluid administration system, such as for subsequent disconnection from an injection system. Nor does the limited backflow reflux valve of the '872 and '074 patents allow a fluid to flow in a reverse direction through or past the valve.
Other injection procedures may require the use of multiple syringes. Additional problems are raised by these injection procedures. The use of multiple syringes not only increases the possibility of backflow from the output to the input due to the increased number of delivery tubes and syringes, but also includes the additional drawback that a first fluid from a first syringe or first delivery tube may undesirably mix with a second fluid from a second syringe or second delivery tube (or alternatively, that air in a first delivery tube may be introduced into fluid in a second delivery tube, and from there into a patient, with possibly drastic consequences). An example of such first and second fluids may be a saline solution and contrast media, which are used during imaging procedures. Saline is normally used during a body pre-scan prior to the injection of contrast media. The pre-scan is used for digital subtraction or superposition of images. This process results in enhancing the final image of a scan. In order to prevent the degradation of the final image, the introduction of contrast media into the saline during the pre-scan procedure should be prevented. However, in fluid administration systems including conduits for both saline and contrast media, the likelihood of mixture of the two fluids is somewhat high due to the configuration of the fluid administration system, as will now be generally described.
In order to include multiple syringes, each having a delivery tube, in a fluid administration system, connectors are often used to direct fluid flow from the multiple input delivery tubes into a single output delivery tube which carries fluid into a patient. Such connectors are widely employed in industrial and medical applications to releasably and lockably interconnect fluid delivery tubes. For example, a first delivery tube for a first fluid like saline and a second delivery tube for a second fluid like contrast media may be placed in fluid communication with one another through the use of a connector. Connectors are often used due to their reliability, their low cost, their ease of assembly, and high pullout forces which resist separation. In particular, the Y-connector is the commonly used shape for introducing fluids in a medical injection system due to the reduction of flow turbulence under high flow rate conditions. Flow turbulence will reduce system performance.
In current injection systems, such as those described above, check valves are disposed within the system to aid in preventing mixing of fluids such as saline and contrast media. The position of the check valve in the injection system determines if any contrast media will be exposed to the saline and delivered during a pre-scan. Normally, the exit side of a check valve will have an area where either air or contrast media can collect. This area may be referred to as a “dead zone.” Since the injection of air is extremely problematic from a patient safety perspective, contrast media is used to remove the air on the exit side of the check valve by flooding the delivery tubes in proximity to the check valve with contrast media. This procedure places contrast media on the exit side of the check valve, which creates the potential for introduction of contrast media into the saline stream, and thus into a subject patient before it is required. Introduction of this contrast media during a pre-scan may alter the final composite image due to false highlighting. In order to prevent degrading the composition image, exposure of the contrast media to saline during the pre-scan phase of an injection procedure should be prevented. However, as described above, with the presence of contrast media on the exit side of the check valve, to prevent air from being injected into a patient, the contrast media mixes with the saline solution during a pre-scan procedure.
This problem of image degradation is further compounded by the fact that there are relatively large dead zones in medical injection systems including connectors. This is because present connectors do not include check valves disposed within the body of the connector. Rather, check valves in present medical injection systems are located in the delivery tubing on the input side of the connector. As a result, a dead zone is present from the exit side of the check valve through any remainder of the input delivery tubing, and through the fluid conduit present in the connector to which the input delivery tubing is connected. As described above, this entire area may be filled with contrast media in order to prevent the introduction of air during an injection. As a result, this relatively large amount of contrast media may be introduced to saline during a pre-scan, thereby degrading the final image.
Thus, it would be desirable to provide a check valve which is normally closed but which may be opened to allow reverse fluid flow to back up a syringe plunger so that catheter placement may be confirmed, and in order to reduce the risk of biohazard resulting from removal of an extension tube to back up the syringe plunger following an injection. It would be further desirable to provide a connector system which prevents air from being injected into a patient and also prevents the mixture of contrast media with saline during a pre-scan procedure.